In a conventional combustion method, combustion is carried out with the aid of a flow of gas formed in a field such that .gradient..times..omega..noteq.0. At present, in order to atomize liquid fuel, a method in which differences in the speeds of fuel and gas are used and a method of directly atomizing fuel by applying pressure thereto are employed. In both of the conventional methods, it is necessary to use a high speed gas flow which is an oxygen source and an atomizing device to burn the fuel. The high speed gas flow accelerates dissipation of heat generated by combustion and of unburned gas and the expansion of gas due to increased temperature increases the amount of external work thus increasing the dissipation of energy to the atmosphere with the result that an excessive amount of fuel is needed to obtain high temperatures. The gas flow is originally unstable. That is, it is unstable in mass and therefore a suitable air-fuel mixing ratio cannot be obtained.
In addition, during combustion, a cooling gas flow is introduced due to convection so that the density, speed and temperature of the gas flow change spatially and with time with the result that temperature change of combustion is uneven. A gas flow where speed is higher in outer than in inner portions makes it impossible for centrifugal force to atomize fuel flowing out to the focal point of the nozzle and, accordingly, the speed difference of the fuel and gas must be employed for atomizing the fuel. In this case, the fuel is only roughly atomized which lowers the combustion efficiency. That is, in combustion using the above-described gas flow, non-adiabatic changes take place in which the entropy is increased making it difficult to improve the combustion efficiency from thermodynamics considerations and the combustion efficiency is much lower than the very high combusion efficiency obtainable with an adiabatic reversible change.